1. Field of the Invention
The present invention relates to an image pickup apparatus, more specifically an image pickup apparatus having a horizontal scanning circuit and a vertical scanning circuit between image receiving areas. In particular, the present invention relates to a radiation image pickup apparatus and a radiation image pickup system, and more particularly to a large-area radiation image pickup apparatus for reading an image utilizing a high energy radiation such as X-ray or gamma-ray.
2. Related Background Art
An image pickup apparatus can be roughly divided into a light receiving area which detects light for example by a photodiode, and a light non-receiving area occupied by peripheral circuits such as scanning circuits.
In the actual image pickup apparatus, the peripheral circuits are often arranged in a light non-receiving area which surrounds an effective pixel area composed of plural light receiving areas.
However, since the peripheral circuits arranged around the effective pixel area composed for example of a single chip gives rise to a limitation in the compactization of the image pickup apparatus, such peripheral circuits have to be provided between the light receiving areas within the effective pixel area.
Also in case of preparing an image pickup apparatus with two or more chips, the effective pixel area has to be formed close to the boundary of each chip in order to increase the resolution at the junction boundary between the chips. For this reason, the light non-receiving area no longer exists around the effective pixel area and the peripheral circuits have to be positioned in the spaces between the light receiving areas which are closely laid down within the effective pixel areas.
In such image pickup apparatus in which the peripheral circuits are positioned in the spaces between the light receiving areas closely laid down within the effective pixel areas, the arrangement of a horizontal scanning circuit and a vertical scanning circuit gives rise to a portion where such horizontal scanning circuit and vertical scanning circuit mutually cross.
FIG. 14 illustrates an example of the layout of the horizontal scanning circuit and the vertical scanning circuit in a conventional image pickup apparatus.
FIG. 15 illustrates another example of the layout of the horizontal scanning circuit and the vertical scanning circuit in a conventional image pickup apparatus. In FIGS. 14 and 15, equivalent components are represented by a same number.
Referring to FIGS. 14 and 15, there are shown a light receiving area (photodiode) 701, a space 702 between the light receiving areas, unit circuits 703-1 to 703-4 of a vertical scanning circuit, unit circuits 704-1 to 704-4 of a horizontal scanning circuit, an area 705 where regularity is lost, and a crossing point 707 of the vertical scanning circuit and the horizontal scanning circuit.
In the conventional example shown in FIG. 14, the unit circuits 703-1 to 703-4 of the vertical scanning circuit are positioned at a constant pitch to maintain a regularity, but, in order to maintain such regularity of the unit circuits 703-1 to 703-4 of the vertical scanning circuit, the unit circuits 704-1 to 704-4 of the horizontal scanning circuit cannot be provided, at the crossing point of the scanning circuits, in the positions where such unit circuits of the horizontal scanning circuit should be positioned in order to maintain the regularity thereof but the unit circuit 704-2 of the horizontal scanning circuit is provided adjacent to that 704-1.
Also in the conventional example shown in FIG. 15, the unit circuits 704-1 to 704-4 of the horizontal scanning circuit are positioned at a constant pitch to maintain a regularity, but, in order to maintain such regularity of the unit circuits 704-1 to 704-4 of the horizontal scanning circuit, the unit circuits 703-1 to 703-4 of the vertical scanning circuit cannot be provided, at the crossing point of the scanning circuits, in the positions where such unit circuits of the vertical scanning circuit should be positioned in order to maintain the regularity thereof but the unit circuit 703-3 of the vertical scanning circuit is provided adjacent to that 703-2.
In the image pickup apparatus in which at least plural light receiving areas are closely laid down as explained in the foregoing, in case of positioning the peripheral circuits in the spaces between such light receiving areas, there inevitably results an area where the vertical scanning circuit and the horizontal scanning circuit mutually cross, and, in order to circumvent such crossing area, the periodicity of the positions of the unit circuits becomes irregular in either of the horizontal scanning circuit and the vertical scanning circuit as shown in FIGS. 14 and 15.
Consequently, a difference in the wiring length induces deterioration of the response characteristics, and the irregularity in the positioning of the unit circuits of each scanning circuit deteriorates the continuity of the pixels, thereby detrimentally affecting the image quality.